U.S. patent number 4,878,215 [Application Number 07/028,604] was granted by the patent office on 1989-10-31 for signal switching system.
This patent grant is currently assigned to Telenex Corporation. Invention is credited to William P. Rogers.
United States Patent |
4,878,215 |
Rogers |
October 31, 1989 |
Signal switching system
Abstract
A system for switching signals travelling between a first set of
multicontact ports and a second set of multicontact ports, in which
the signals at the contacts of each of the first ports are sampled
by a parallel-to-serial multiplexer to form a corresponding single
serial multiplexed signal. Each such serial multiplexed signal is
applied to a matrix switch of the type having a switching device at
each cross-point, and each of the output signals from the matrix
switch is supplied to a serial-to-parallel demultiplexer. Each such
demultiplexer supplies its reconstructed separate parallel signals
to its associated port in the second set of ports. By controlling
the conduction status of the switching devices in the matrix, the
desired connection of each of the first set of ports to the desired
one of the second set of ports is accomplished, with many fewer
switching devices than would otherwise be required.
Inventors: |
Rogers; William P.
(Collingswood, NJ) |
Assignee: |
Telenex Corporation (Mount
Laurel, NJ)
|
Family
ID: |
21844376 |
Appl.
No.: |
07/028,604 |
Filed: |
March 20, 1987 |
Current U.S.
Class: |
370/366;
370/535 |
Current CPC
Class: |
H04L
12/525 (20130101) |
Current International
Class: |
H04L
12/50 (20060101); H04L 12/52 (20060101); H04Q
011/04 (); H04J 003/12 () |
Field of
Search: |
;370/110.1,58,112,85,53
;340/826,825.79,825.8 ;379/248 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Orsino; Joseph A.
Assistant Examiner: Scutch, III; Frank M.
Attorney, Agent or Firm: Free; Albert L.
Claims
What is claimed is:
1. A signal-switching system, comprising:
a plurality of groups of input signal lines each carrying on one of
its lines a data signal and on a plurality of its other lines
signals relating to said data signal
a plurality of time multiplexers each connected to a corresponding
different one of said groups of input signal lines and each
producing a stream of time-multiplexer serial-bit signals
corresponding to the signals on said corresponding groups of input
signal lines;
a plurality of serial-to-parallel time demultiplexing means each
responsive to any of said streams of time-multiplexed serial
signals supplied thereto to produce a corresponding group of
separate reproduced parallel signals substantially the same as
those carried by that one of said groups of input lines connected
thereto;
cross-point signal switching means connected between all of said
multiplexers and all of said demultiplexers and controllable to
supply any one of said streams of serial-bit signals directly, and
without storage, substantially instantaneously from the multiplexer
producing it to any selected one of said plurality of
time-demultiplexing means without changing the order of bits in
said streams; and
means for supplying said reproduced parallel signals from each of
said time-demultiplexing means to a corresponding one of said
groups of signal utilization lines.
2. The system of claim 1, wherein said cross-point signal switching
means comprises a matrix switch having a plurality of input
terminals supplied with respective different ones of said
time-multiplexed serial-bit signals from said plurality of
multiplexers, a plurality of output terminals connected to
respective different ones of said plurality of demultiplexers, and
electrically controllable switching elements for connecting any
selected one of said input terminals to any selected one of said
output terminals of said switching means.
3. The system of claim 1, wherein each of said groups of input
signal lines comprises an RS-232 port, and the signals on the
contacts thereof are in RS-232 format.
Description
BACKGROUND OF THE INVENTION
There are many important applications in the electronics art
wherein it is highly desirable, or necessary, controlledly to
connect one or more multiple contact source ports to one or more
signal utilization ports in any desired combination. In some cases
it may be desirable to control the connection of a single source
port to any of a plurality of signal utilization ports or to
connect any of a plurality of source ports to one signal
utilization port, but in general there may be a plurality of both
source ports and signal utilization ports to be controlledly
interconnected.
The problem with providing such controlled switching becomes
increasingly more difficult as the number of source ports and/or
signal utilization ports is increased, and the problem becomes
particularly severe when the number of signals in each port is
large. For example, the standard RS-232 port provides 24 signals
(plus ground), one of which typically carries a serial data signal
and the others of which typically carry auxiliary information, for
example timing and control signals for effecting the desired
communication of the serial data signal. While in some cases all 24
of the signals need not be utilized, even when less than all of the
signals are used the complications of the switching operation can
become unduly burdensome. Where the switching system is to be of
most general utility the problem is most severe, in that it should
be able to provide controlled switching of all 24 of the port
signals since, in a given situation, any one of the signals or all
of them may be utilized. If, as is not unusual, there are 128
source ports and 128 utilization or destination ports, it would be
necessary to provide a matrix having 393,216 crosspoint switching
elements to effect the desired switching by conventional means.
Accordingly, other methods of accomplishing such switching have
been proposed and employed, including the time-division
multiplexed-bus switch in which the source and the destination
ports are all connected to a common bus containing a line for each
corresponding contact of the ports, so that by turning on any
selected source port and any selected destination port at the same
instant, the desired communication can be accomplished momentarily
for any selected pair of such devices. Since communication is
desired between all source devices and destination devices, each of
the destination devices is switched on momentarily and repetitively
when each of the source device is switched on, in time-multiplex
fashion. In order for this to be effective, especially with signals
embodying high data rates, the switching must be accomplished at
extremely high rates. For example, if a 9600 baud signal is to be
transferred with no more than 12.5% distortion, then it must be
sampled at least 76,800 times per second. If 256 such sets of
signals are to be switched over the same bus, then the aggregate
sampling rate of the bus must be at least 19,660,800 samples per
second. More signals, higher speeds, and lower distortion all
require even higher sampling rates on the high speed bus so that
the overall performance of this type of switching is limited by the
bandwidth that is available on the high speed bus.
The present invention provides a signal switching system which is
not subject to the bandwidth limitations of the above-described
time-multiplexed common bus system, and which does not require the
large number of switching elements required by the standard matrix
switching also described above.
It is therefore an object of the present invention to provide a new
and useful signal switching system.
Another object is to provide such system which does not require the
large number of switching elements or the high bandwidth required
of previous systems for accomplishing comparable switching.
SUMMARY OF THE INVENTION
These and other objects of the invention are achieved by the
provision of a signal switching system for controlled connection of
any source port to any signal utilization port by converting the
source signals from each source port into a single serial
time-multiplexed signal prior to its application to the switching
system, applying each serial time-multiplexed signal to the
switching system. and then demultiplexing each signal to convert it
back to its original parallel form after it leaves the switching
device. This greatly decreases the number of switching devices
required in the switching system; for example, where the number N
of separate signals at each source port is the same as the number N
of signals at each signal utilization port, the number of switching
elements required is decreased by a factor N, for example by a
factor of 24 if there are 24 signals or contacts in each port and
the signals are unidirectional. If the signals are bidirectional
(i.e. travel in both directions between the connected ports), then
the number of switching elements is decreased by N/2, in this
example by 12. At the same time, the system is not subject to the
bandwidth restrictions of the multiplexed-bus type of switching
arrangement described previously.
The multiplexing and demultiplexing required is preferably provided
by means of the plug-contained multiplexers and demultiplexers
described in detail in my co-pending application Ser. No. 803,894
filed Dec. 2, 1985, wherein each multiplexer or demultiplexer is
contained in the casing of a plug which also mounts the contacts
designed to mate with the source port or the destination port, so
that the desired multiplexing and demultiplexing is accomplished by
merely plugging the line into the appropriate source or destination
port. An extremely effective form of this system which results from
the combination of the plug-contained multiplexer-demultiplexer
lines with the simple form of matrix switch described generally
above is described in more detail hereinafter.
BRIEF DESCRIPTION OF FIGURES
These and other objects and features of the invention will be more
readily understood from a consideration of the following detailed
description, taken with the accompanying drawings, in which:
FIG. 1 is a schematic diagram showing an elementary form of matrix
switching system according to the prior art;
FIG. 1A is a schematic diagram showing a system according to the
invention for performing the same overall function as the prior art
system of FIG. 1;
FIG. 2 is a schematic diagram of another form of prior art
switching system;
FIG. 2A is a schematic diagram of a switching system according to
the invention, for performing the functions of the system of FIG.
2;
FIG. 3 is a schematic diagram of another switiching system
according to the prior art;
FIG. 3A is a schematic diagram according to the invention for
performing the functions of the system of FIG. 3;
FIG. 4 is a schematic diagram of another switching system according
to the prior art;
FIG. 4A is a schematic diagram of a system according to the
invention for performing the function of the system of FIG. 4;
FIG. 5 is a schematic diagram of a switching system according to
the invention as applied to the switching of connections between a
plurality of computer front ends and a plurality of modems; and
FIG. 6 is a schematic diagram illustrating a preferred circuit
arrangement for controlling each of the switching devices in the
matrix system of the invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Referring now to the conventional switching system shown in FIG. 1,
a source port S.sub.1 presenting five separate signals S1A, S1B,
S1C, S1D and S1E on five corresponding output lines 10, 12, 14, 16
and 18, one for each of the separate output signals; a signal
utilization port U.sub.1 is provided with five corresponding input
lines 20, 22, 24, 26 and 28. Assume that it is desired to be able
to connect the output lines of S1 to, or disconnect them from, the
input lines to U.sub.1. To this end, the two sets of lines 10-18
and 20-28 each may be connected to a maxtrix switching system 26,
which includes five controllable switching devices 30, 32, 34, 36
and 38, each disposed between one of the lines from the source
S.sub.1 and a particular corresponding one of the lines connected
to the utilization device U.sub.1. It is noted that even in this
simple, rudimentary switching operation, five switching devices are
required. Such arrangements are common in the prior art.
FIG. 1A shows a system employing the same signal source S.sub.1 and
the same signal utilization device U.sub.1. In accordance with the
present invention, the five signals from S.sub.1 are supplied to a
first multiplexer M.sub.1, which samples them sequentially to form
on its output line 40 a serial time-multiplexed version of the
separate input signals thereto. Output line 40 is connected to the
switching system 42, as is the single line 44 leading to a
demultiplexer DM.sub.1, the output of which feeds the utilization
device U.sub.1. Switching system 42 consists of a single
controllable switch device 48, controllable to connect or isolate
lines 40 and 44 with respect to each other.
In operation then, if it is desired to supply the five signals at
S.sub.1 to U.sub.1, the switching device 48 is closed, the
serial-time multiplexed signals on line 40 are thereby supplied to
the input line 44 to demultiplexer DM.sub.1, and the Iatter device
supplies to U.sub.1 the five reconstructed signals corresponding to
those from source S.sub.1. The overall objective of controlling
whether or not the signals from S.sub.1 are supplied to U.sub.1 is
accomplished with a switching system requiring only a single
switching device, rather than the five required in the prior art
system, for a reduction of 5:1 in switching devices.
FIG. 2 illustrates the corresponding case in which five signals on
five output lines of S.sub.1 may be switched to utilization port
U.sub.1 or to utilization port U.sub.2, as desired. The switching
system shown for accomplishing this is a simple conventional matrix
switching system, as provided by the prior art, in which each of
the five output lines from S.sub.1 is connectable to either a
corresponding line leading to U.sub.1 or to a corresponding line
leading to U.sub.2, by actuating the appropriate ones of the
switching devices to their closed or open conditions in appropriate
well-known manner.
FIG. 2a shows an arrangement according to the present invention
corresponding to the basic type of system shown in FIG. 2. Here the
same source S.sub.1 supplies its five output signals to a
parallel-to series multiplexer M.sub.1 and the output of the
multiplexer is fed to switching system 50 over line 51. The
utilization devices U.sub.1 and U.sub.2 are connected separately to
the switching system 50 by way of respective series to parallel
demultiplexers DM.sub.1 and DM.sub.2 and lines 53 and 54. Only two
switching devices 55 and 56 are required in the switching system to
provide the desired switch control action, compared with the ten
required in the prior art arrangement of FIG. 2, for a 5:1
reduction in the number of switching devices.
FIGS. 3 and 3A illustrate, respectively, a system according to the
prior art and a system according to the present invention by means
of which either the source port S.sub.1 presenting five signals or
the source port S.sub.2 presenting five different signals may be
connected to the single signal utilization device U.sub.1. Again,
the conventional arrangement of FIG. 3 utilizes a simple switching
matrix system using ten switching devices such as 57.
The system of FIG. 3A utilizes two different parallel to serial
multiplexers M.sub.1 and M.sub.2 connected to the respective
sources S.sub.1 and S.sub.2, and a single serial to parallel
demultiplexer DM.sub.1 supplying the signal utilization device
U.sub.1. The switching system comprises a simple matrix utilizing
only two switching devices 68 and 70, which connect either the
output of M.sub.1 or of M.sub.2 to the input of DM.sub.1. The 5:1
saving in switching complexity will be apparent here also.
FIGS. 4 and 4A illustrate systems according to the prior art and
according to the invention, respectively, which approach a little
more closely those which are of more commercial interest. In this
case, there are a plurality of source ports (S.sub.1, S.sub.2) and
of utilization devices (U.sub.1, U.sub.2). In the prior art
arrangement of FIG. 4, the switching sYstem is again a simple
matrix utilizing twenty switching devices such as 58, while in the
arrangement of FIG. 4A according to the invention, the arrangement
utilizes two parallel to serial multiplexers M.sub.1 and M.sub.2
and two serial to parallel demultiplexers DM.sub.1 and DM.sub.2 ;
the switching system itself is a simple matrix utilizing only four
switching devices such as 59, which enable either the output of
M.sub.1 or the output of M.sub.2 to be supplied to the input of
either DM.sub.1 or DM.sub.2. The reduction in number of switching
devices is again 5 to 1.
It will be understood that the specific arrangement illustrated in
FIGS. 4 and 4A is still of far less complexity than is often or
generally involved in a commercial situation. As mentioned above, a
commercial system using 128 RS-232 source ports and 128 RS-232
utilization ports, each having 24 lines or contacts, would
conventionally require 393,216 cross-point switching elements,
while using the present invention only 12,288 or 24 times less are
required.
FIG. 5 shows in more detail a type of commercial system in which
the invention has more practical application. FIG. 5 shows computer
front end A and front end computer B, and it is assumed that there
are a large number of similar computer front ends to be
accommodated. Each computer front end is provided with two ports,
which may be of the RS-232 type. Also shown are modems A, B, C and
D each connected to respective telephone lines (not shown) for
external communication. The system shown permits any one of the
four modems (or any of a large number of additional modems, not
shown for convenience) to be connected to any one of the front-end
ports of computers A or B, or to any other computer front ends
which may be employed.
The system of FIG. 5 as shown permits communication in either
direction between modem and computer front end, that is, a signal
maY travel from modem to computer or from computer to modem through
a suitable channel for each direction of transmission. To permit
this the system uses at each modem port and at each front-end port
a cable multiplexer C/M such as is described in my copending
application Ser. No. 803,894 filed Dec. 2, 1985, which provides
such duplex action within a plug adapted to be plugged into an
RS-232 port.
The switching system then provides the desired controlled two-way
connection between each computer front-end port and the port of any
selected one of the modes. It comprises in this example the
standard switching boards (SSB's) 82, 84, 86 and 88 which provide
conversion in either direction between the balanced-pair lines
preferably used in the two-wire cables connecting the switching
system to the modems and cable multiplexers, and the single-wire
and ground system used within the switching system. The SSB's may
also provide some of the switching action. The standard matrix
boards (SMB's) 90, 91, 92 and 93 are interconnected in any suitable
conventional manner to provide the remaining necessary switching
action. Preferable one switch is used for communication in one
direction and another for communication in the other direction.
The switch elements are preferably on chips, and controlled by the
chassis controller boards (CCB's) 94 and 95, which in turn may be
controlled by a system controller 98, which may be based on an IBM
PC-XT.
FIG. 6 shows the basic arrangement of a typical switching chip in
the matrix, assuming a grid of 16 input lines Y1 to Y16 and 16
output lines X1 to X16. Each input line is provided with an input
receiver such as 100, 102 and each output line is provided with an
output driver such as 106, 108. The switching device is in each
case a transmission gate such as 110, controlled by a flip-flop
such as 162, from the external controller. Only one such
arrangement is shown, but it will be understood that one such
arrangement of flip-flop and transmission gate is used for each
cross-point switching device.
While the invention has been described with particular reference to
specific embodiments in the interest of complete definiteness, it
will be understood that it may be embodied in a variety of forms
diverse from those specifically shown and described.
* * * * *